TaOx-Capped Pt Nanoparticles As Active and Durable Electrocatalysts for Oxygen Reduction

Here we demonstrate the formation of unique structure of TaO_x-capped Pt nanoparticles on a Pt/TaOx/GC electrocatalyst (Fig. 1), where at first tantalum oxide (TaO_x)and next Pt nanoparticles were electrodeposited on the glassy carbon (GC) substrate, for an oxygen reduction. The surface characterizations show that the nanoparticles of TaO_x deposit homogeneously on the GC surface, forming a thin layer and surprisingly, the Pt nanoparticles do not exactly deposit on the top layer of the TaO_x, i.e., Ta₂O₅ but inside their framework and consequently a unique assembly of the TaO_x-capped Pt particles is fabricated. The analyses using XPS spectra indicate electronic interactions of TaO_xwith the GC, as well as with the Pt nanoparticles. The electrochemical measurements conducted by cyclic voltammetry and rotating ring-disk electrode voltammetry reveal that the novel electrocatalyst possesses an enhanced activity for an oxygen reduction reaction, without any loss of performance even after 250,000 cycles (1,111 h) of a durability test. The plausible reasons for the remarkable activity and durability of this electrocatalyst are proposed.

 Fig. 1 Schematic illustrations of (a) Pt deposited on a TaO_x-modified GC surface with a TaO_x framework, (b) O₂ adsorption on Pt-TaO_xinterface and (c) bonding formation of Ta with GC and Pt.

Acknowledgement

The present research was financially supported by Grant-in-Aid for Scientific Research from the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan.

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